When Bronx homemaker Monique Sykes decided to fight what she believed was a shady debt collector, she thought she was the only victim.

Six years later, Sykes and 355,000 other New Yorkers have achieved a far-reaching class-action settlement against three defendants: Leucadia National Corp. and other debt-buying units of $11.88 billion holding company Leucadia Corp., law firm Mel S. Harris and Associates and process server Samserv.

In addition to paying $59 million, the defendants agreed to exit the debt-collecting business and work with New York’s Office of Court Administration to wipe out roughly $800 million in questionable debts, from default judgments.

The defendants did not admit any wrongdoing.

A widespread practice known as “sewer service” lies at the heart of Sykes’ case. That’s the term for what happens when debt collectors fail to properly notify consumers of lawsuits, then falsify court papers asserting a valid case.

When the consumer doesn’t appear in court, the debt collector wins by default and can then freeze the consumer’s bank account or garnish wages to collect. an unverified debt. The effects can be devastating, particularly on the low-income households most often hit with these suits.

“The due process was skipped,” said Sykes.

Ariana Lindermayer, a lawyer with MFY Legal Services, one of three firms representing the plaintiffs, compared the allegedly false court papers in consumer credit cases to the robosigned foreclosure documents that rocked the mortgage industry five years ago.

Lawyers for Mel S. Harris and Samserv did not respond to requests for comment. A Leucadia spokesman said the company “had no role in the practices alleged in the complaint,” which predated Leucadia’s 2013 merger with the Jefferies investment bank.